1. Field
Example embodiments relate to a light emitting device fabricated using wafer bonding and a method of fabricating the light emitting device using wafer bonding.
2. Description of the Related Art
The advantage of light emitting diodes (LEDs) using a semiconductor material, e.g., a Group III-V nitride semiconductor, is that LEDs may be relatively small and lightweight and have a relatively long lifespan. A variety of technologies have been developing so as to increase efficiency of LEDs. High output and high brightness LEDs have recently attracted attention to be used as an illumination apparatus. However, in a case where a relatively high power is applied to LEDs for relatively high output, the efficiency of LEDs is reduced compared to that of a case where lower power is applied thereto.
Vertical LEDs having a high efficiency in applying current thereto have been proposed. Unlike horizontal LEDs in which a part of a semiconductor layer is etched and electrodes are formed in the etched portion of the semiconductor layer, electrodes are directly disposed on upper and lower surfaces of a semiconductor layer in vertical LEDs, and thus current may be efficiently applied from electrodes to the semiconductor layer. Therefore, vertical LEDs may obtain enhanced efficiency and output compared to horizontal LEDs. Also, vertical LEDs are more easily cooled compared to horizontal LEDs, thereby more easily dissipating heat generated during operation.
Vertical LEDs in which electrodes are disposed on the upper and lower surfaces of the semiconductor layer require a different fabrication process from horizontal LEDs. For example, after growing the semiconductor layer on a growth substrate, e.g., sapphire, the growth substrate needs to be removed so as to perform the remaining processes (i.e. subsequent processes). In this regard, before removing the growth substrate, the semiconductor layer is bonded onto another substrate so as to support the semiconductor layer from which the growth substrate is removed. Such bonding is performed in a wafer scale, which is referred to as wafer bonding.
A tensile stress is generated in the semiconductor layer during a cooling process. When the growth substrate on which the semiconductor layer is formed is bonded to a transfer wafer, wafer may be warped due to the tensile stress during the cooling process after wafer bonding, and cracks may occur in the semiconductor layer. If the growth substrate is removed, the tensile stress in the semiconductor layer may increase. Accordingly, a manufacturing yield of LEDs may be reduced.